The present invention relates to a multilayered ceramic type electromagnetic coupler for effecting the transmission of signals in an electrically insulated state by means of electromagnetically inductive action.
In a signal transmission circuit using a printed circuit or the like, there are cases where it is necessary to effect the transmission of signals with electrical insulation provided between two apparatuses for the purpose of elimination of noises or the like, and electrically insulated transformers and photo-couplers are conventionally used extensively as means for achieving this purpose.
Among the aforementioned means, the transformer has the advantage that signals to be transmitted can be covered in a wide range from a low frequency to a high frequency. However, since the transformer has a structure in which two or more types of coils are generally wound around a core, and its transmission characteristics improve with an increase in the number of turns of the coil, the apparatus tends to become very large in scale, resulting in increased production costs.
On the other hand, if a photo-coupler is used, since an input circuit and an output circuit is effected by optical coupling without electrically coupling them. Furthermore, since the transmission of signals is unidirectional, there is no need to take the unexpected feedback of signals into consideration. Thus, the photo-coupler has various advantages. However, these characteristics of the photo-coupler are exhibited on the precondition of transmission of binary digital signals. In the transmission of analog signals, drawbacks are encountered in terms of the temperature characteristic, the dynamic range, and so forth. For this reason, the photo-coupler can be used in a very limited range in the transmission of analog signals.